155  
FXUS65 KBYZ 140838  
AFDBYZ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BILLINGS MT  
238 AM MDT FRI MAY 14 2021  
   
DISCUSSION
 
 
TODAY THROUGH SATURDAY NIGHT...  
 
THE UNSETTLED WEATHER PATTERN WILL CONTINUE THE NEXT COUPLE OF  
DAYS. WEAK SHORTWAVE ENERGY AND UPPER DIVERGENCE WITHIN A  
SLUGGISH NORTHWEST FLOW WILL AFFECT THE REGION AND BE ABLE TO  
TRIGGER SCATTERED SHOWERS AND THUNDERSTORMS. LOW LEVEL FLOW HAS  
TURNED A BIT UPSLOPE AND WILL MEAN THE BEST CHANCE OF  
PRECIPITATION IS FOR THE WESTERN AND CENTRAL ZONES TODAY AND  
TONIGHT. AN UPPER LOW WILL SWING INTO SOUTHERN CALIFORNIA ON  
SATURDAY AND THIS SHOULD RESULT IN THE BULK OF SHOWERS BEING OVER  
THE MOUNTAINS AND SOUTHERN BORDER AREAS FOR THE FIRST PART OF THE  
WEEKEND. KEEP IN MIND, ALTHOUGH WEAKER FLOW ALOFT WILL MEAN POP  
AND DROP TYPE CONVECTION, SLOWER STORM MOTION COULD ALSO RESULT IN  
HIGHER RAIN AMOUNTS FOR LUCKY LOCATIONS. OVERALL, THE PATTERN  
LOOKS PRETTY TYPICAL FOR MAY, WITH MAINLY AFTERNOON AND EVENING  
CONVECTION, AND TEMPERATURES IN THE MID 60S TO MID 70S. BT  
 
SUNDAY THROUGH FRIDAY...  
 
GOOD MODEL CLUSTER AGREEMENT WITH UPPER RIDGING OVER THE AREA  
SUNDAY THROUGH MONDAY, WITH BASICALLY DRY WEATHER AND TEMPS  
WARMING INTO THE 80S ON MONDAY. UPPER LOW TAKES SHAPE OFF THE  
PACIFIC NW COAST ON TUESDAY WHILE RIDGING REMAINS OVER THE AREA.  
INCREASING SW FLOW WILL BRING ISOLATED SHOWERS AND THUNDERSTORMS  
TO THE MOUNTAINS AND FOOTHILLS WITH CONTINUED TEMPS IN THE 80S. SW  
FLOW CONTINUES INCREASING AHEAD OF THE PACIFIC NW LOW ON  
WEDNESDAY, AND PRECIPITATION CHANCES INCREASE TO SCATTERED OVER  
THE MOUNTAINS/FOOTHILLS WITH ISOLATED SHOWERS AND STORMS OVER THE  
PLAINS. CLUSTERS SHOWED VARIOUS SW FLOW SOLUTIONS FOR THURSDAY.  
THE ECMWF ENSEMBLE MEAN HAD THE UPPER LOW MOVING INTO THE REGION  
ON FRIDAY, WHILE THE GEFS MEAN HAD A NEGATIVELY TILTED TROUGH.  
THUS, SCATTERED SHOWERS AND THUNDERSTORMS ARE FORECAST OVER THE  
AREA THU. THROUGH FRIDAY WITH TEMPS STILL ABOVE NORMAL, BUT IN  
THE 70S. NOTED THE EC ENSEMBLE METEOGRAMS PUT IN SOME GUSTY WINDS  
LATE IN THE PERIOD AS THE SW FLOW ALOFT INCREASES, AND THE NBM DID  
REFLECT STRONGER WIND GUSTS DURING THIS TIME AS WELL. ARTHUR  
 

 
   
AVIATION
 
 
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL OVERSPREAD  
THE AREA FROM W TO E THIS AFTERNOON. A FEW MOUNTAIN SHOWERS WILL  
OCCUR THIS MORNING. CHANCES FOR SHOWERS AND THUNDERSTORMS WILL  
GRADUALLY DECREASE FROM N TO S THIS EVENING. EXPECT MVFR/IFR  
CONDITIONS IN THE PRECIPITATION, WITH AREAS OF MOUNTAIN  
OBSCURATION THIS AFTERNOON AND EVENING. ARTHUR  
 

 
   
PRELIMINARY POINT TEMP/POPS
 
 
TDY SAT SUN MON TUE WED THU  
-------------------------------------------------------  
BIL 069 046/071 046/077 049/084 054/083 054/080 053/076  
4/T 32/T 11/U 00/U 11/U 22/T 33/T  
LVM 067 044/069 042/075 045/081 048/079 047/076 046/070  
4/T 33/T 11/U 01/U 11/U 24/T 34/T  
HDN 070 044/072 044/077 047/084 051/084 052/081 052/079  
2/T 22/T 11/U 00/U 11/U 12/T 23/T  
MLS 070 044/073 045/077 049/084 054/085 054/081 054/078  
2/T 11/B 11/U 00/U 01/U 11/U 23/T  
4BQ 068 046/070 046/074 049/079 053/082 052/079 054/077  
2/T 13/T 11/U 01/U 01/U 11/U 22/T  
BHK 069 042/072 044/075 047/080 050/082 050/078 051/075  
2/T 02/T 11/U 00/U 01/U 12/T 23/T  
SHR 064 042/066 041/072 043/078 047/079 047/075 048/074  
3/T 25/T 21/U 01/U 11/U 12/T 23/T  
 

 
   
BYZ WATCHES/WARNINGS/ADVISORIES
 
 
MT...NONE.  
WY...NONE.  
 

 
 

 
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